Method and apparatus for sharpening drills



June 25, 1957 E. J. BUSHEY ETAL METHOD AND APPARATUS FOR SHARPENING DRILLS Filed Dec. 28, 1951 3 Sheeis-Sheet l INVENTORS ESMONDE J. BUSHEY JOHN N. ENGELSTED ATTORNEYS June 25, 1957 E. J. BUSHEY EIAL METHOD AND APPARATUS FOR SHARPENING DRILLS Filed Dec. 28, 1951 3 Sheets-Sheet 2 INVENTORS ESMON DE J. BUSH EY BY JOHN N. ENGELSTED ATTORNEYS INVENTORS ESMONDE J. BUSHEY ENGELSTED wifia ATTORNEYS E J BUSHEY ETAL 2,796,703

METHOD AND APPARATUS OR SHARPENING DRILLS 3 Sheets-Sheet 3 JOHN N. BY

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June 25, 1957 Filed Dec. 28, 1951 Patented June 25, 1957 METHOD AND APPARATUS FOR SHARPENING DRILLS Esmonde 5. Bushey, Athol, and John N. Eugelsted, Petershazn, Mass., assignors to Union TwistDrill Company, Athoi, Mass a corporation'of Massachusetts Application December 28, 1951,-Serial No. 263,861

18 Claims. (Cl. 51-96) The present invention relates to the grinding of drill points and is concerned more particularly with an improved method and' apparatus by which drill points may be ground rapidly and accurately in a fully automatic sequence of operations.

Prior methods of grinding the points of twist drills have generally involved advancing the drill in the direc tion of its axis into contact with an abrasive wheel while rotating or rocking the drill. Such methods require accurate support of the drill in proper angular relation to the grinding surface, as well as precise coordination of the feed of the drill relative to the rotation or rocking movement thereof, if the drill point is to be correctly formed.

In most cases, drill grinding is carried out on machines using plain grinding wheels with the grinding, done either on the periphery or on the side of the wheel. In certain instances, however, abrasive wheels'with V-shaped grooves have been utilized, with the drill advanced into the groove radially of the wheel.

It is the object of the present invention to provide a still further improvement'in. the art of drill point sharpening, whereby the drill may be presented to the wheel in a novel manner which permits the point to be sharpened rapi ly and accurately. More specifically, the invention concerns a method andmachine which are especially suited for automatic operation, whereby drills may be presented to the grinding wheel in rapid succession by fully automatic means and in such fashion that the points are precisely shaped.

In the present invention, a V-grooved grinding wheel is employed, with the drillpresented to the wheel by passing. the drill point bodily through the groove, the drill point making contact with the sides of the wheel groove during said passage. Advantageously, although not necessarily, the drill is passed through the wheel groove in a forward stroke and return, with the drill preferably con-- tacting the wheel on both the forward and the return passage. Thus, the drill may be loaded automatically into a workholder at a loading station, after which the workholder is actuated to carry the drill point to the wheel and through the V-groove while contacting the sides, the workholder thenbeing returned to the loading station with the drill point passing through the V-groove on said return stroke. The presenting of the point to the wheel may be effected by rocking movement of the drill, by relative translational movement, or as in the illustrative embodiment, by a combination of rocking and translational movements between drill and wheel.

In addition to the novel method of presenting the drill to the grinding wheel, the invention includes as features a novel loading and chucking mechanism by which the drills may be accurately positioned in the workholder preparatory to the grindingstep. A further feature involves the workholding chuck itself, whereby the chuck is enabled to operate satisfactorily'even though exposed to the abrasive particles from the grinding: operation.

In the drawings illustrating the several features of the novel method and apparatus, Fig. 1 is a view in front elevation showing the upper or principal portion of the machine; Fig. 2 is a top plan view thereof; Fig. 3 is a sectional view in elevation of the automatic loading and workholding portions of the machine, the view also serving to illustrate the manner of presenting the drill to the grinding wheel; Fig. 4 is a view in elevation, partly in section, showing the mounting of the workholder and the actuating means by which the drill is caused to be presented tothe' grinding wheel-in accordance with the novel method of the invention; Fig. 5 is" a detail View, partly in section, taken on the line 5-5 of'Fig. 3 with the loading. quill in engagement with the drill and illustrating the position of the drill at the end of the loading stroke, and Fig. 6 is a schematic diagramshowing the connections for the control'switches and solenoid-actuated valves.

In general, the machine comprises two main sections, a lower section containing. the grinding wheel and itsdriving and positioning means and an upper section comprising the workholding andloading means. The grindiug Wheel indicated at 8 is journaledin a carrier 10 having. a dovetailed base portion 12 received in. ways forming a part of the machine base I4. By means of hand wheel 16, the grinding wheel may be moved axially across. the machine frame to bring one or another of the multiple V-grooves' in itsv periphery into proper alignment with. the drill point to be ground. A flat belt 2% and wide. pulley 22 provide driving connections. fromthe motor 24 while permitting the adjustment of the grinding wheel and its carriage in the machine frame.

I The upper section of the-machine comprises-a supporting frame or table 28 pivotally secured at. one end to apedestal 30', with the otherend adapted tobe raised or' lowered betweenvertically slotted'pedestals32. A clamp nut 34 having a lever arm 35 serves to lock the framesecurely in adjusted position, after the. precise height wise adjustment of the table has been: obtained by thumbscrew 36 with the aid of dial gauge 38.

The workholding chuck indicated generally at 40* is mounted at the end of a shaft 42 journaled in" bearings for rotation about an axis parallel to'the axis of'rotation of the grinding wheel. As indicated in Figure 3, the chuck is arranged to receive a drill from. a magazine 44 or other source of supply of drills to be sharpened, a drill being slid into the open chuck when the latter is' in a horizontal position in alignment with the bottom drill in the magazine. As will hereinafter more fully appear, the drill is positioned in the chuck with high accuracy, both in respect to the amount of drill tip exposed and in respect to the position of the flutes. Immediately upon completion of the loading operation, the chuck is swung downwardly to carry the drill-point through the \/-groove in the rotating grinding wheel, the chuck moving to a position slightly past the perpendicularas shown'in dotted outline in Figure 3-. The chuck then. swings back to a horizontal position, with: the drill point again contacting the grinding wheel at the bottom of the swing. Upon reaching horizontal position, the chuck opens to release the drill, and the insertion of the nextdrill to be ground carries the previously sharpened drillout through the rear end of the chuckto suitable collecting and conveying means, not shown.

The mechanism bywhich the workholder is caused to rock through it's arc of operation of slightly over90 degrees comprises a pneumatic actuator cylinder having a piston rod 52. The outer end of'the' piston rod carries a fitting 54 pivotally connected-to a lever 56 secured to a sleeve 58 mounted in coaxial relation to the shaft 4 2 To accommodate the arc of. movement of the lever 56, the pneumatic cylinder 50 is pivotally mounted at 59'- inavbracket 60 on the support 28;

To provide accurate adjustment of the position of the chuck at the limit of its swing upon its return to horizontal position for receiving work, adjustable stop screw 62 is arranged to contact bracket 64 (see Fig. 2). To control the rate of movement of the chuck in its swing, a check cylinder 66 is mounted adjacent the actuating cylinder, said check cylinder having a piston rod 68 provided with adjustable abutments 70 which are engaged by the upstanding forked projection from fitting 54- carried by actuator piston rod 52. An adjustable check valve 72 controls the degree of damping or dash pot action. a

The rocking movement of lever arm 56 is transmitted to the chuck supporting shaft 42 by means ofa pin extending through a slot in a collar 82 secured to said shaft 42. This construction permits a supplementary lateral oscillation to be imparted to the chuck and drill independent of the principal rocking movement by which the drill point is carried into and through the V-groove of the grinding wheel.

This lateral oscillation, which results in multiple contacts of the drill point with the sides of the V-groove alternately during the brief period of engagement in the swing through the groove, is imparted by means of a cam or eccentric 86 driven through a speed reducer 88 from a. belt 90 connected to the main driving motor 24.

A cam follower 92 is mounted in a yoke 94 having a stub shaft 96 received within the hollow end of a workholder shaft 42. A vertical pin 98 extends downwardly intoa slot in fixed plate 100 to prevent the yoke and roll from rotating out of proper operative position relative to the cam 86 during the rocking movement of shaft 42.

To transmit the reciprocatory movement generated by cam 86, the upwardly projecting portion of pin 98 is engaged by shoulder 102 on collar 82. As shown in Fig. 2, the shoulder has a slight relief so that when the chuck has completely returned to its horizontal position, the pin 98 is off the high portion of the shoulder so that the lateral position of the chuck is independent of theparticular position of the cam 86. Instead, the position of the chuck is determined by a collar 108 the position of which may be accurately set on the shaft 42 by reason of the threaded engagement plus locking set screw. A spring 110 serves to urge the shaft and chuck firmly to the left as viewed in Fig. 4 so as to follow the cam motion during the time the chuck is swinging through the wheel and to insure that the chuck is brought to the limit of its inward movement, with the collar engaging the end of sleeve 58 when the actuating pin 98 is off the high portion of the shoulder on collar 82.

The loading mechanism by which the drills are inserted in the chuck in precisely the correct positionis illustrated in detail in Fig. 3. A magazine 44 having a vertical channel in which the drills are stacked one above the other in single row is mounted on support 116 so that the drill at the bottom is aligned with the chuck opening when the chuck is in its horizontal position. A set screw 118 permits accurate vertical adjustment of the magazine 44 relative to the support 116 and chuck 40.

To carry the bottom drill of the stack into the chuck, a quill 120 is arranged to be reciprocated through the bottom of the magazine, the quill being provided with a forked tip the prongs of which enter into the drill flutes to provide a positive, non-rotating grip between quill and drill, as shown in Fig. 5. Apertures at the bottom of the magazine are aligned with the lowermost drill to provide passage for the quill at one end and for the drill exit at the other. Inserts 122 of hardened steel serve to support the parts accurately during the operation. A leaf spring 124 provides frictional drag on the drill to insure positive gripping of the drill flutes by the quill. 7

The quill is actuated longitudinally and at the same time rotated by means ofa spirally grooved arbor carried in sleeve 132. A pin 134 has a pointshaped to fit within the groove to bring about the rotary movement as the arbor advances. The arbor is driven longitudinally by means of a pneumatic cylinder having a piston rod 142, the end of which is mounted in a carriage block 144 sliding along ways 146 formed in the frame 28. A ball bearing 148 permits free rotation of the arbor 130 during the stroke of the piston rod 142. A dash pot cylinder 150 has its piston rod 152 coupled to the piston rod 142 of the air cylinder by a bracket 154 to control the velocity of the stroke.

To insure that the drill rod is correctly positioned in the workholding chuck, the arbor 130 is adjustable in respect to both its longitudinal and its rotational position at the end of its advance. The stroke distance is detert mined by means of a collar 156 mounted by means of screw threads on the arbor 130, the collar 156 coming up against the end of sleeve 132 to provide a positive limit to the forward stroke. The rotational position of the quill 120 at the end of the stroke is adjusted by rotating the sleeve 132 within its supporting bracket 160, with a set screw 162 to secure the sleeve once the proper setting has been obtained.

The workholding chuck 40 is of conventional construction, employing a piston to effect the closing of the collet 172 when air under pressure is supplied through flexible hose connection 174. To avoid the wear that would normally occur due to the entry of abrasive particles into the chuck mechanism, provision is made for effectively flushing the chuck parts. To this end, fluid such as fresh coolant is supplied to the chuck interior through connection 176 via a flexible hose, not shown. The. coolant or other fluid flows outwardly through the various passages in the chuck including the collet, so as to flush away and prevent entry of the abrasive particles thrown off by the grinding operation. To minimize leakage of coolant from the rear of the chuck and to provide a frictional drag on the drill, a flattened sleeve 178 of a resilient material such as a suitable synthetic rubber is secured at the rear, through which the drills are ejected.

The operation of the machine is carried out in a predetermined sequence of steps under the control of switches which, through solenoid-actuated valves of usual construction, control the admission of air to the actuating cylinders and to the chuck. The switches are mounted to respond to the movement of the parts, being in the nature of limit switches so that the completion of one part of the cycle serves to initiate the next step in the sequence of operations.

To this end, switches 180 and 182 are mounted to be actuated by lever 56 at the limit of the rocking stroke of the chuck 40. These switches, like the other switches to be referred to, are of the type responsive to slight movement of an exposed actuator. A second set of switches 190, 192 is mounted to be actuated at the limits of the stroke of the quill 120, the switches being mounted on the frame 28 to be engaged by projections 194, 196 on carriage 144. Another switch 200 is mounted intermediate switches 190, 192 for actuation by a pivotally mounted cam block 202 during the retracting stroke only of the arbor-actuating carriage. The connections for said switches are shown diagrammatically in Fig. 6.

Through the use of conventional solenoid-actuated valves 204, 206, the air supply to the cylinders 50 and 140, respectively, is controlled by said switches according to the following sequence of steps: Assuming that the driving motor 24 has been started and the grinding wheel 8 set in the proper axial position, the first operation is to admit air to cylinder 140 to cause the quill 120 to ad- Vance a drill into the unlocked chuck 40. As soon as the carriage reaches the limit of its stroke, switch is actuated to reverse the stroke and cause the carriage and quill to return to retracted. position. At the same time, air is admitted to the chuck 40 to cause piston 170 to advance on the collet and clamp the drill.

In the course of the return stroke of carriage 144, and

immediately following the disengagement of quill 120 from the drill in the chuck, switch 200 is actuated by cam block 262. Said switch is connected to the solenoid of the valve in control of cylinder 50, and actuation of the switch results in initiating the rocking movement of chuck 46 to carry the drill point through the V-groove in the grinding wheel. As a result of the oscillating or reciprocating movement imparted by cam 86, the lips of the drill are caused to contact the sides of the V-groove in the wheel alternately, so as to minimize heating effects and to avoid the necessity of advancing the drill into the bottom of the V-groove where a sharp point could not readily be obtained.

After the chuck has been rocked to carry the drill point beyond the wheel, switch 182 is engaged by arm 56 to cause a reversal of stroke and return the chuck to horizontal position, the drill again making alternate contacts with the wheel at the bottom position (Fig. 3) to impart a finish grind to the lips. It will be observed that the mode of presenting the drill to the wheel results in the lips being ground to an arcuate profile of radius equal to the radius of swing of the drill about the Work-holder shaft 42, with proper clearance rearwardly of the cutting lips by reason of the fact that the drill is presented to the wheel in substantially the position shown in end view, Fig. 5.

Upon completion of the return stroke of the chuck, switch 180 is engaged by arm 56. This serves to release the air from the chuck and unlock the collet 172. At the same time, the valve to cylinder 140 is openedto initiate a work loading stroke by quill 120, with the quill advancing into the chuck the next drill to be sharpened While pushing ahead of it the previously sharpened drill, the latter emerging from the chuck at the opposite end. At the limit of the quill stroke, the switch 190 is actuated, as previously described, to reverse the stroke and retract the quill, after which the drill is swung into contact with the grinding wheel, as before.

The cycle of operations is thus carried out in a fully automatic rapid sequence in which the completion of one step is required before the next step can occur. The manner in which the loading operation is performed permits the drill to be accurately positioned in the chuck, so that the drill points are accurately and uniformly ground during the swing through the V-groove.

While the invention has been illustrated and described in terms of a particular embodiment wherein both the rocking and the lateral translational movements are imparted to the drill, it will be understood that the invention may be embodied and practiced in other forms and constructions within the scope of the appended claims.

We claim:

1. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in the periphery thereof, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, drill supporting means, mechanism for actuating the drill supporting means to carry the drill point bodily through the V-groove in the wheel, and means for eifecting relative lateral movement between drill point and wheel for causing the point to contact the sides of the V-groove alternately during the passage of the point through the groove.

2. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in the periphery thereof, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, drill supporting means, mechanism for actuating the drill supporting means to carry the drill point bodily through the V-groove in the wheel, and means for oscillating the drill supporting means laterally of the wheel to cause the drill point to contact the sides of the V-groove alternately during the passage of the point through the groove.

3. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in the periphery thereof, means for rotatably supporting the grinding 'wheel, driving means for rotating the wheel,

drill supporting means, mechanism for rocking the drill support to swing the 'drill point through the V-groove in.

the grinding wheel, and means for effecting relative lateral movement between the drill point and the wheel for causing the point to contact the sides of the V-groove alternately during the swing of the point through the groove."

drill disposed radially of said rocking axis, and means for rocking the drill to carry the point thereof through the V-groove in the grinding wheel.

5. Apparatus for grinding the points of twist drills,

comprising a grinding wheel having a V-groovein the' periphery thereof, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, means for supporting a drill for rocking movement about an axis parallel to the axis of the grinding wheel with the drill disposed radially of said rocking axis, means for rocking the drill to swing the point thereof through the V- groove in the grinding wheel, and meansfor reciprocating the drill body along the rocking axis to cause the drill to contact the sides of the V-groove alternately.

6. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in the periphery thereof, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, means for'supporting a drill for rocking movement about an axis parallel to the axis'of the grinding'wheel with the drill disposed radially of said rocking axis, means for rocking the drill to swing the point thereof through the V- groove in the grindingwheel andback through the groove to the starting point of the swing, and means for reciprocating the drill laterally of the wheel during the swing to' cause the drill point to contact the sides of the groove alternately on both the forward and return swings. of the drill point through the wheel.

7. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in its periphery, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for holding a drill in operative relation to the wheel, means for supporting the chuck for rocking movement about an axis parallel to the wheel axis, means for automatically chucking a drill to be ground with the drill in predetermined longitudinal and rotational position within the chuck, and power-operated means for causing the chuck to swing the drill point through the groove in the wheel and back to starting position.

8. Apparatus for grinding the pointsof twist drills, comprising a grinding wheel having a V-groove in its periphery, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, means for supporting a drill to be ground comprising a chuck, means for introducing a drill into the chuck in predetermined longitudinal and rotational position comprising a quill having a forked drill-engaging end, an arbor for advancing and simultaneously rotating the quill, and stop means for bringing the quill to rest with the forked end in predetermined rotational and axial position, means for securing the drill in the chuck upon insertion, and means operative upon completion of the drill loading operation for moving the chuck in a path to cause the drill point to pass through the V-groove in the grinding wheel in grinding relation to the sides of the V-groove.

9. Apparatus for grinding the points of twist drills comprising a grinding wheel having a V-groove in its periphery", means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for supporting a drill to be sharpened, means for supporting the chuck for rocking movement about an axis parallel to and spaced from the grinding wheel axis, means for introducing a drill into the chuck in predetermined longitudinal .and rotational position, means operative upon completion of the loading operation for causing the chuck to swing about its supporting axis to carry the drill point into and through the V-groove in the grinding wheel and for thereafter swinging the chuck back to its initial loading position, and means operative after the chuck has left its loading position for reciprocating the chuck 1 laterally of the grinding wheel to cause the drill point to contact the sides of the V-groove alternately.

10. Apparatus for grinding the points of twist drills comprising a grinding Wheel having a V-groove in its periphery, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for supporting a drill to be sharpened, a shaft for supporting the chuck for rocking movement about an axis parallel to'and spaced from the grinding wheel axis, means for introducing a drill into the chuck in predetermined longitudinal and rotational position, means operative upon completion of the loading operation for causing the chuck to swing about its supporting axis to carry the drill point into and through the V-groove in the grinding wheel and for thereafter swinging the chuck back to its initial loading position, and means for reciprocating the chuck bodily in a direction axially of its supporting shaft during the swing of the drill through the V-groove in the grinding wheel, said means comprising cam and cam follower means, and connections between the cam follower and the chuck supporting shaft for operatively connecting the follower and shaft during the wheel-engaging portions of the swing and for disengaging the shaft from operative relation with the cam follower upon return of the chuck to loading position to provide a predetermined chuck loading position independently of the cam and cam follower.

llfAutomatic loading and-chucking mechanism for introducing a fluted drill in a chuck in predetermined longitudinal and rotational position comprising a quill having a forked drill-engaging end, an arbor for advancing and simultaneously rotating the quill to cause the forked end of the quill to engage the flutes of the drill tip, stop means for bringing the quill to rest with the forked end in predetermined rotational and axial position, and means for securing the drill in the chuck while the drill is positioned by the quill.

12. Apparatus for grinding the points of fluted drills comprising a grinding wheel, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for supporting a drill to be ground, and means for loading a drill into the chuck in predetermined longitudinal and rotational position comprising a quill having a forked end to engage the flutes at the tip of a drill, an arbor for advancing and simultaneously rotating the quill about an axis aligned with the chuck, stop means for bringing the quill to rest in predetermined rotational and axial position with the drill within the chuck means for clamping the drill in the chuck while the drill is positioned by the quill, means for disengaging the quill from the drill end, and means for effecting relative movement between chuck and grinding wheel to bring the drill tip into operative contact with the grinding wheel.

' 13. Apparatus for grinding the points of fluted drills comprising a grinding wheel, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for supporting a drill to be ground, and means for loading a drill into the chuck in predetermined longitudinal and rotational position comprising a quill having a forked end to engage the flutes of the workengaging tip of a drill, an arbor for advancing and simultaneously rotating the quill about an axis aligned with the chuck, stop means for bringing the quill to rest in predetermined rotational and axial position with the drill within the chuck, means for securing the drill in the chuck while positioned by the quill, means for disengaging the quill from the drill tip, and means for moving the chuck from drill-loading position into operative position with the drill tip in contact with the grinding wheel.

I 14. The method of grinding the point of a twist drill which comprises rotating a grinding wheel having a V- groove in its periphery, swinging a drill to be ground bodily about an axis parallel to and spaced fromrthe grinding wheel axis to carry the drill point through the V-groove, and simultaneously reciprocating the drill bodily from side to side to cause the point to contact the sides of the groove alternately during the swing.

15. The method of grinding the point of a twist drill which comprises rotating a grinding wheel having a V- groove in its periphery, swinging a drill to be ground bodily about an axis parallel to and spaced from the grinding wheel axis to carry the drill point through the V-groove, and simultaneously efiecting relative lateral reciprocatory movement between wheel and drill to cause the drill to contact the sides of the V-groove alternately during the passage through the groove.

16. Apparatus for grinding the points of twist drills, comprising a grinding wheel having a V-groove in its periphery, means for rotatably supporting the grinding wheel, driving means for rotating the wheel, a chuck for holding a drill in operative relation to the wheel, means for supporting the chuck for movement in a plane per- .pendicular to the wheel axis, means for automatically chucking a drill to be ground with the drill in predetermined longitudinal and rotational position within the chuck, and power-operated means for causing the chuck to move the drill point through the groove in the wheel and back to starting position.

17. Apparatus for grinding the points of fluted drills comprising a grinding wheel, means for supporting the grinding wheel, means for rotating the wheel, a chuck for supporting a drill to be ground, means (for loading a drill into the chuck in a predetermined longitudinal and rotational position comprising a quill having an end to engage the tip of a drill, an arbor for advancing the quill about an axis aligned with the chuck, stop means for bringing the quill to rest in predetermined position with the drill within the chuck, means for clamping the drill in the chuck while the drill is positioned by the quill, means for disengaging the quill from the drill end, and means for efiecting relative movement between the chuck and grinding wheel to bring the drill tip into operative contact with the grinding wheel.

18. Apparatus for grinding the points of fluted drills comprising a grinding wheel, means for supporting the grinding wheel, means for rotating the wheel, a chuck for supporting a drill to be ground, means for loading a drill into the chuck in a predetermined longitudinal and rota tional position comprising a quill having a forked end to engage the flutes at the tip of a drill, an arbor for advancing and simultaneously rotating the quill about an axis aligned with the chuck, stop means for bringing the quill to rest in predetermined rotational and axial position with the drill within the chuck, means for clamping the drill in the chuck while the drill is positioned by the quill, means for disengaging the quill from the drill end, and means for eflecting relative movement between the chuck and grinding wheel to bring the drill up into operative contact with the grinding wheel.

References Cited in the file of this patent.

UNITED STATES PATENTS (Other references' on following page) UNITED STATES PATENTS Knapp Mar. 16, 1943 Kronwall July 22, 1947 Hanford Oct. 14, 1947 Fouquet Aug. 2, 1949 5 Grube Jan. 2, 1951 Lentz Mar. 6, 1951 10 FOREIGN PATENTS Great Britain Oct. 10, 1911 Sweden Sept. 29, 1949 

